ScienceShot

ScienceShot: Martian Meteorite Full of Bits of Black Glass

Nomads scouring the Moroccan desert have recovered fragments of a meteorite seen blazing across the sky on 18 July 2011. Analyses of those pieces, from a meteorite dubbed Tissint after a village in the region where the stones landed, reveal that the parent object had been blasted from Mars long ago. Many other martian meteorites have been collected, but this émigré from the Red Planet is only the fifth ever collected after it was seen falling to Earth, the researchers report online today in Science. The largest known fragment (above) weighs about 1.1 kilograms and, like many meteorites, is covered by a black veneer created during the stone's plunge through Earth's atmosphere. Unlike all but one other martian meteorite, however, many of the small cracks in the fragment contain bits of black glass (the black veins and pepperlike bits exposed on the broken surface of the meteorite). That glass formed when material that had eroded from the martian surface was melted by the impact that lofted material into space about 700,000 years ago. The presence of short-lived radioactive forms of several elements created when the meteorite was exposed to cosmic rays during its interplanetary trek to Earth—especially vanadium-48, which has a half-life of about 16 days—indicate that the fragments are associated with the recent meteorite fall, the researchers say.